1. Field of the Invention
The invention relates to a supply pump having a driven impeller which rotates in a pump housing, the impeller having at least one ring of vane chambers, and the supply pump having a partially annular channel which is arranged in the wall of the pump housing lying opposite the ring of vane chambers and extends from an inlet channel to an outlet channel, the cross section of the partially annular channel having a plurality of sections.
2. Description of the Prior Art
Supply pumps of this type are frequently used as fuel pumps and are known from practice. The design of the cross section of the partially annular channel with a plurality of sections is intended to enable the supply chamber, which is composed of the partially annular channel and the vane chambers, to be adapted to the circulating flow produced therein. In the case of the supply pump known from practice, at least one of the sections has a flat side, so that the circulating flow is at an alternating distance from the wall of the partially annular channel.
A disadvantage of the known supply pump is that at the transitions of the sections, and therefore in the regions in which the circulating flow is at a particularly large distance from the wall of the partially annular channel, vortices arise which result in a severe reduction in the efficiency of the supply pump.
In order to avoid the turbulence, a supply pump which is disclosed in U.S. Pat. No. 5,375,971 includes a cross section of the supply chamber designed as part of an ellipse, the depth of the partially annular channel being less than half of the minor axis of the ellipse. By this means, flat sections are avoided in the region of the supply chamber. However, the disadvantage of this supply pump is that turbulence arises in the partially annular channel, in the inlet region and in the outlet region of the circulating flow, since the supply chamber forms tapering pockets particularly in regions which are adjacent to the vane chambers, and the circulating flow is therefore at a variable distance from the wall of the partially annular channel. Furthermore, the elliptical design of the cross section of the partially annular channel can be manufactured only with very great difficulty.